MAIL AND DIRECTORY MIGRATION
Allow the addition of empty groups to Notes
Groups selected for import are considered empty if they do not contain any members who can be registered in Notes. By default, Domino Upgrade Services do not import empty groups. A group may be empty because it contains no members -- for example, an obsolete group that was never removed from the address book; or the group may not contain any local users -- for example, an e-mail distribution list that lists only the Internet addresses of users on other mail systems.

Migrating a group whose members are not available -- and that would therefore, be empty -- results in an entry in the Domino Directory that serves no useful purpose. Set this option only if you intend to add users to any empty groups either during registration or after registration completes.